S-816A34AMC-BAJT2G SII [Seiko Instruments Inc], S-816A34AMC-BAJT2G Datasheet - Page 14

• Manufacturer Part Number: S-816A34AMC-BAJT2G
• Description: EXTERNAL TRANSISTOR TYPE CMOS VOLTAGE REGULATOR
• Manufacturer: SII [Seiko Instruments Inc]

14
EXTERNAL TRANSISTOR TYPE CMOS VOLTAGE REGULATOR
S-816 Series
2. External Adjustment of Output Voltage
The detection of the overcurrent is done by the sense resistance (R
When Tr1 comes on, triggered by a voltage drop of R
to the time constants of the capacitor (C
the "L" level, and the regulating operation to stop, and interrupting the current to the load.
When the load current is cut off, the voltage drop of R
the NPN transistor (Tr2) off.
In this condition, the shutdown pin returns to the "H" level, according to the time constants of the
capacitor (C
"L" level is the time in which the load current remains cut off.
If an overcurrent flows again after the shutdown pin has assumed the "H" level following the delay time
and the regulating operation has been restarted, the circuit will again suspend the regulating operation
and resume the intermittent operation. This intermittent operation will be continued till the overcurrentt is
eliminated, and once theovercurrent disappears, the normal operation will be restored.
The overcurrent detection value (I
In this case, R
saturation voltage of Tr1.
For the PNP transistor (Tr1) and the NPN transistor (Tr2), try to select those of small-signal type that offer
a sufficient withstand voltage against the input voltage (V
The on-time (t
following equations:
In this case, V
V
Set the on-time value that does not cause the overcurrent protection to be activated by a rush current to
the load capacitor. Then, compute the ratio between the on-time and the off-time from the maximum
input voltage of the appropriate application and the power dissipation of the external PNP transistor, and
decide the off-time with reference to the on-time established earlier.
Take the equation above as a rough guide, because the actual on-time (t
defined and checked using the utilizing components.
The S-816 Series allows you to adjust the output voltage or to set its value over the output voltage range
(6 V) of the products of this series, when external resistances R
illustrated in Figure 13. Moreover, a temperature gradient can be obtained by inserting a thermistor or
other element in series with external resistances R
I
t
t
SH
OUT_MAX
ON
OFF
denotes the inversion voltage ("L"→"H") of the shutdown pin.
= −1 × C
= −1 × C
V
IN
= |V
1
) and resistance (R
2
+
−
BE1
ON
BE2
S
1
× R
× R
denotes the resistance value of the sense resistance, and V
) and the off-time (t
C
| / R
denotes the base-emitter saturation voltage of Tr2, V
IN
2
1
ON/
× L
× L
S
N
OFF
N
( 1 − ( V
( 1 − V
VIN
1
SH
BE2
). This delay time in which shutdown pin returns to the "H" level from the
OUT_MAX
/ V
OFF
× ( 1 + R
IN
) of the intermittent operation are broadly expressed by the
Seiko Instruments Inc.
EXT
Error
amplifier
)
2
) and resistance (R
) is represented by the following equation:
Figure 13
2
+
−
/ R
VSS
3
V
A
) ) / ( V
REF
and R
S
S
, the NPN transistor (Tr2) also comes on, according
stops. This makes Tr1 off again, and also makes
R
R
IN
IN
B
1
2
).
.
− V
2
). This causes the shutdown pin to turn to
VOUT
BE1
A
, R
) )
S
B
) and the PNP transistor (Tr1).
and capacitor C
IN
C
denotes the input voltage, and
ON
C
) and off-time (t
BE1
denotes the base-emitter
R
R
A
B
C
are added, as
+
−
OFF
OUT
C
Rev.5.1
L
) should be
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